The travel writer Bruce Chatwin, in order to commune with nature, was known to hike naked. Sometimes he would tie flowers around his private parts.

In his intensely strange and terrifically vivid new book, “Being a Beast: Adventures Across the Species Divide,” the English naturalist Charles Foster occasionally removes his clothes as well. He hopes to understand what it might feel like, out in the wild, to be a badger, an otter, a fox, a deer or a swift.

Sometimes he is, to borrow the title of a television show, naked and afraid. Mostly he is merely cold and irritably witty. “Being a Beast” reads like what you might get if you took a writer like Julian Barnes or Anthony Lane and dropped him into the woods with only a granola bar and a pointy stick.

“Being a Beast” is about Mr. Foster’s “rewilding,” his efforts to “grope at extreme otherness.” He lives for six weeks alongside badgers in a hill in Wales. Like an otter, he tries to snatch fish with his teeth.

When he behaves like an urban fox in London, strangers think he is a lunatic. He arranges to be hunted by bloodhounds, as a deer might be. He becomes dreamy about swifts (birds that resemble swallows) while nibbling on their favorite insects, as if they were winged mixed nuts.

“Nature writing has generally been about humans striding colonially around, describing what they see from six feet above the ground,” Mr. Foster writes. In this book, he gets distressingly close to the earth. He breathes deeply of the peaty soil, so deeply you fear he will inhale a fire ant.

If neuroscience has recently taught us a good deal about how the brains of animals function, Mr. Foster says, “the literary adventure has barely begun. It is one thing to describe which areas of a badger’s brain light up on a functional M.R.I. scanner as it sniffs a slug. It is quite another to paint a picture of the whole wood as it appears to the badger.”

It is still another to pry a flattened squirrel off the road, as Mr. Foster does in the badger chapter, along with his young son, and eat the thing cooked “with wood sorrel and wild garlic.”

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In his new book, “Being a Beast,” the naturalist Charles Foster mimics animal behavior.CreditJoshua Lott for The New York Times

Mr. Foster is humble about the limitations of his project. He tries to avoid the pitfalls of traditional nature writing, such as anthropocentrism (believing humans are the planet’s central species) and anthropomorphism (attributing human traits and emotions to animals). “Of course I have failed,” he adds.

His awareness of his failures makes him all the more winning. He decides it has been ridiculous to grow his toenails long, for example, in imitation of a deer’s hooves. Deer have hard lives. “There was no point in not cutting my toenails,” he comments, “if I couldn’t also be persecuted from the beginning of time.”

Mr. Foster builds a case that it is important and, indeed, oddly humanizing to try to get close to nature. You may find yourself in agreement while being glad it’s him out there, not you.

He taste-tests worms. (“Worms from the high Kent Weald are fresh and uncomplicated; they’d appear in the list recommended with a grilled sole.”) He defecates here and there to mark territory. He shoots down rapids and crawls through grass. He turns over a piece of fetid pizza with his nose. He vomits grass, shrubs and leaves into his mouth to approximate a feel for chewing cud.

Mr. Foster is a veterinarian who teaches medical law and ethics at the University of Oxford. He can come across like a frenzied hippie, but he arrives at his embrace of animal ways from a somewhat more sober perspective: that of a serious former hunter.

“I bought my daughter a .410 shotgun when she was 10,” he writes. “I whipped in to beagles, rode to foxhounds and staghounds, and had a monthly column in The Shooting Times. My name is in gold-embossed game books in some nice country houses.” He regrets some of his former blood lust.

He is aware of himself as a hunter in other, less expected, ways. If you want to be a wolf, he tells us, here is what to do: Go to a good school and study laissez-faire economics.

Here’s his interpretation of what was said to his class when it graduated: “You’re about to leave Cambridge, gentlemen. Now, it may very well be true that the meek will inherit the earth, but my advice to you is this: Until they show some signs of making a serious bid for that position, trample all over them.”

As this quotation makes plain, this is not a typical nature book. Mr. Foster will go far out of his way to make a stray point, or especially to make a joke. He takes his topic seriously enough to hazard not being taken seriously at all.

This book traffics in loathing as well as fear. Mr. Foster hates otters, for example. He describes them as wretched furry worms (“invaders, not citizens”) that bite off each other’s testicles. His dislike heats his prose up nicely.

The closest he can legally get to being an otter, he says, “is to stay up for a couple of nights, drinking a double espresso every couple of hours, before having a cold bath followed by a huge breakfast of still-twitching sushi and then a nap, and then keep repeating until I die.”

There are moments in this book when Mr. Foster is as antic as an otter. His whiskers get twitchy; he can try too hard to entertain. Such moments are relatively few. “Being a Beast” strikes me as an eccentric modern classic of nature writing. It is packed with wriggling pleasures.

If the author’s physical excursions put you in mind of the actor David Naughton running naked through the woods in “An American Werewolf in London,” his mental excursions are just as breathless. We happily follow him until he is, as he puts it near the end, “a gnat’s breath away from psychosis.”

Being a Beast

Adventures Across the Species Divide

By Charles Foster

235 pages. Metropolitan Books. $28.

A version of this article appears in print on , on Page C1 of the New York edition with the headline: A Writer Gets Close to Nature (Very Close). Order Reprints | Today’s Paper | Subscribe